MISCONCEPTIONS CONCERNING THE BEHAVIOR, FATE AND TRANSPORT OF THE FUEL OXYGENATES TBA AND MTBE

The release of gasoline from underground storage tanks and the subsequent appearance of dissolved constituents in drinking water has focused attention on the use of MTBE in reformulated fuels. Biodegradation of MTBE in soil, photo-oxidation in the atmosphere or chemical oxidation during remediation of gasoline releases can produce the intermediate tertiary butyl alcohol (TBA). TBA is also a fuel oxygenate and can be found as a co-product in MTBE synthesized from methanol and TBA. Because the physical properties of ethers and alcohols differ somewhat from the predominant hydrocarbon compounds in gasoline, misconceptions have developed about the behavior of fuel oxygenates in storage and in the subsurface. Critical review of several misconceptions about MTBE and TBA in gasoline reveals the concepts were conceived to rationalize early field observations and/or incomplete data sets. Closer scrutiny, in light of recent laboratory investigations, field data, case studies and world literature, clarifies these misconceptions and assumptions about the behavior of ether oxygenates and their degradation products in the environment. Commonly held myths focus on four general areas of fuel and fuel oxygenate management: storage/dispensing, hydrology, remediation, and health effects. Storage/dispensing misconceptions address materials stability to ethers in fuel and the environmental forensics of fuel systems failure. Groundwater and hydrology myths deal with plume dynamics and the impact of fuel on drinking water resources. Remediation myths focus on the performance of traditional hydrocarbon remediation technologies, recent developments in biodegradation and natural attenuation, drivers of remedial design and remediation costs. Health effects myths address both acute and chronic exposure risk evaluations by national and international health agencies. MTBE and TBA are manageable by the same processes and precautions used for gasoline and other fuel hydrocarbons.